Dehumidifier



May 20, 1952 J. w. cAsE DEHUMIDIFIER Fild Jan. 11, 1950 INVENTOR. JAIME Vi, $55

Patented May 20, 1952 kLUN'ITED S 1.0 F E 3,596,979

'1, F DEHUMIDIFIER James W. Case; Fairfax, Va.

;'-:.;Application-.lanuary '11,;195Q,'Serial ,No..:138-,ll41

1"(Granted Jinderxthe act-' of'fMa'rclr 3; :1883,=.:as iaamended. April .30, 1'928;-.'370.;0;..-G. i157) 2 Claims.

""Thepresent invention 1 relates to dehumidify- "*ing'devices and more particularly to devices for removing and excluding moisture from chambers or containers such as casings for instruments whereby fungus growth andcorrosion due to moisture may=be inhibited. A feature of said in- "-vention-resides in the provision of' novel means for reactivating" moisture adsorbing materials employed therewith.

Heretofore dehumidifying devices for such use havecomprised a desiccant, such assilica gel or theiike, suitably supported to permit air circulation therethrough. Suchdesiccantmust be frequentlyreplaced. This is'objectionable and such "i-t'dehumidifiers" are particularly unsatisfactory for use' -with.aircraft instruments since the rapidly :ifiuctuating temperature and "pressure conditions 'to"whichisucl'r'instruments"are subjected increase "'air circulationtand accelerate saturation "of the desiccant.

.To avoidsuchdificulties it has heretofore been necessary to enclose delicate aircraft instruments in hermetically sealed cases. It has further been necessary to construct the instrument cases of "materials 'sufliciently strong to withstand pres-' sure extremes so that the cases will not be crushechor warp'ediflflhis increasesthe Weight of the instruments, and ..difiiculty is encountered when the. cases must be openedto service the instrument enclosed therein.

Hence. an'object of the present invention is to .-.pro'vide.a-new and improved type of dehumidifier 1 for removing and excluding. moisture frominstruements.

.Anotherobject of the invention is .to-provide a dehumidifier for substantially closed bodies wherein means are provided for increasing the effective life of a desiccant employed therewith before said desiccant must be reactivated.

Another object of the invention is to provide an instrument dehumidifier having in combination therewith a breather tube which is so arranged and constructed as to initially exclude a substantial portion of the moisture suspended in the air breathed through the tube.

Another object of the invention is to provide means for reactivating regenerable desiccants employed in dehumidifiers.

Other objects and their attendant advantages will become apparent as the following detailed description is read in coniunction with the accompanying drawings wherein:

Fig. 1 is a cross-sectional view partly in elevation showing one embodiment of the present invention applied to an instrument case;

- Fig. 2 is atransverse=section partly in elevation "taken on alinesubstan-tially corresponding. to line 2-2ofFig.-1;and

Fig. 3 is a'schematic view of a circuit incorporated in the device of the present invention.

which-may be secured by'means of a suitably gsealedflange' M to theexterior wallfof the case.

-Within the housing:I3-'anc l spacedfrom the in- 'terior' wall thereof is adesiccant container l5 which may comprise a pair -of spaced concentric cylindricalpperforated shells I 6 and l iiwhich are adapted to contain between. their adjacent-surfaces agregenerable desiccant l8 suchias silicagel or the like. ,Ifrdesired', the desiccant l8: maybe :molded-ih the. form of a"suitableycylinderand substituted for the container l5--provided the desiccantis a. moldable type such as activated "alumina; Seals l9.and'-20;are located'atopposite ends 'of .thecontainer I 5 to provide asealed .space' 2| from which the circulating air must pass through the desiccant.

A breather tube'nlwhichis exposed to. the 'atmosphere at one end;23 leads a substantialdistance, into the housing. I5 andterminates at 24 in the space 2|, asshowni" The breatherptubegfl forms an important feature'of the .presentinvention since I have found that the amount'ofmoisture that. williidiffuse. through such. a tubeis a function, of the .1ength andmthe cross-sectional areaof that tube." I have found furtherlthat by providing a breather tube 22, having a length more than ten times its inside diameter, in this dehumidifier, atmospheric moisture is substantially prevented from entering the instrument case I!) during periods when no breathing occurs through the tube, such as during static atmospheric conditions, while an instrument In may be stored or held in a standby condition. I have found further that, as inbreathing occurs into instrument In, as would happen when an aircraft descends from a high altitude to a low altitude, a substantial portion of the atmospheric moisture will be completely removed as the air passes through the desiccant l8 and enters the instrument case l0. Hence, by providing a dehumidifier with a breather tube of proper dimensions as aforesaid, an instrument with which the dehumidifier may be used can breathe naturally in accordance with changes in ambient temperature and pressure conditions and still be protected against atmospheric moisture at all times.

Means for reactivating the desiccant are provided and this means will now be described. Imbedded in the desiccant I8 is an electric heatin element 25 which may comprise a stretched coil of resistance wire, appropriately sheathed as shown, or bare. Electrically connected in parallel with the heating element 25 is a blower motor 26 (Fig. 3), adapted to drive a blower 21 which is connected by a suitable passageway 28 with the central hollow portion 29 of the dehumidifier as shown. Mounted on the blower 21 is an outlet valve 30 which is adapted to open only during the outflow of air therethrough.

When it becomes necessary to reactivate the desiccant l8, a switch means 32 is operated, either manually or automatically by means of a humidostat, time switch, or the like, to simultaneously energize the heating element 25 and the blower motor 26. Any convenient current source may be used, for example, a battery 3! or an ordinary alternating or direct current outlet. The heat generated by the element 25 will cause desorption of the desiccant l8 and the blower 21 will draw reactivating air from the outside atmosphere through the dehumidifier and discharge the liberated moisture to the atmosphere.

When the blower is started, air from the outside atmosphere is drawn through the breather tube 22 to the space 2|, which serves as a manifold for equal distribution of the atmospheric air to the desiccant l8, thence through the desiccant 18 where temperature rise permits the air to absorb moisture being liberated from the desiccant, thence into the space 29 and again to the outside atmosphere via the passageway 28, the blower 21 and outlet valve 30. Thus a rapid reactivation of the desicant will be accomplished without removing it from the dehumidifier and without exposing the instrument case ill to the moisture present in the dehumidifier during the reactivating process.

It should, of course, be noted that, if desired, the reactivating means aforesaid may be connected directly in the power circuit of such electrical instrument as may have been housed in the case l0. Then while the instrument is in use, (electrically energized) the desiccant will maintain the delicate parts of the instrument dry and operable and the reactivating means will maintain the desiccant IS in an activated state. Later, should a static condition occur, as when the instrument is put in storage, is shipped or assumes a standby condition, immediate protection is available due to the adsorption capacity of the desiccant l8.

Obviously modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specified.

The invention described herein may be manuiactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A dehumidifying device for controlling moisture conditions within a substantially closed chamber without preventing ingress of outside air comprising; a housing, said housing having an air admitting aperture, 9. desiccant within the housing arranged in the form of a barrier so as to divide the housing into two concentric chambers, a tube communicating with said aperture said tube being of a length at least ten times its internal diameter, the inner end of said tube terminating in one of said chambers, the other of said chambers being adjacent and in direct communication with the space in which dehumidifying conditions are to be maintained.

2. A dehumidifier for controlling moisture conditions within an enclosed space comprising a housing, a desiccant within the housing, said desiccant dividing the housing into two concen tric chambers, an air ingress port comprising a moisture inhibiting diffusion tube of a length at least ten times its internal diameter, one end of said tube extending through the housing to communicate with the outside air and the other end terminating within one of said chambers, the other of said chambers being in direct communi cation With the enclosed space to permit the diffusion of dehumidified air therebetween, and means for reactivating the desiccant.

JAMES W. CASE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,443,435 Rohrer Jan. 30, 1923 1,726,805 Carrey Sept. 3, 1929 1,863,656 Hartman June 21, 1932 2,283,043 Busch May 12, 1942 2,399,971 Wolfe May 7, 1946 2,471,376 Peters May 24, 1949 2,471,442 Morf May 31, 1949 

